Method for propagating vibration into a conductive fluid and method for solidifying a melted metal using the same propagating method of vibration

ABSTRACT

A given magnetic field and a given wave are applied to a conductive fluid so as to satisfy the relations of: 
       l   ⊥ &gt;δ  ( 1 ) 
     λ″&gt;λ  ( 2 ) 
     on condition that a length of said conductive fluid is set to l ⊥ (m), and the equations of δ=(2/Pμω) 1/2  and λ″=2πB/ω(ρμ) 1/2  are defined (σ: the electric conductivity (S/m) of said conductive fluid, ρ: the density (kg/m 3 ) of said conductive fluid, μ: the permeability of said conductive fluid, B: the strength of said magnetic field (T), ω: the angular frequency of said wave), thereby to generate and propagate a given vibration into said conductive fluid.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to a method for propagating vibration intoa conductive fluid and a method for solidifying a melted metal using thesame propagating method of vibration.

[0003] 2. Description of the Prior Art

[0004] The control of solidification structure and the refinement can beperformed effectively by applying vibration into the melted liquid metalto be solidified. For example, it is well known that solidificationprocess is started by applying mechanical impact to a supercooled liquidmetal. It is also well known that fine structure can be created byapplying vibration to a melted liquid metal during solidification anddegasifying process is promoted by applying compress ional wave to amelted liquid metal.

[0005] On laboratory scale, by applying a given mechanical vibration tothe whole of a vessel where a liquid metal is charged, a given vibrationcan be easily applied to the liquid metal. On large industrial scale,however, it is difficult to vibrate the whole of a huge vesselmechanically. Therefore, as of now, such an attempt is made as toposition a magnetostrictive oscillator or an electrostrictive oscillatorin a liquid metal, and thus, apply a given vibration to the liquidmetal. Also, such an attempt is made as to introduce a compressionalwave which is generated by a speaker into a liquid metal and thus, applya given vibration to the liquid metal.

[0006] However, if such a magnetostrictive oscillator or anelectrostrictive oscillator is employed, it may be melted or destroyedin the liquid metal, to contaminate the liquid metal. Also, theamplitude of the vibration to be applied is restricted due to thelimitation of the output power level of the oscillator. Moreover, ifsuch a compressional wave is employed, it may be reflected almostentirely at the boundary between the liquid metal and the environmentalatmosphere, not to be applied to the liquid metal because the acousticresistance between the liquid metal and the environmental atmosphere isincreased. As a result, a method for propagating vibration into a liquidmetal is not be developed particularly on the large industrial scale, atpresent.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide a new methodfor propagating vibration into a liquid metal, which is usable on alarge industrial scale.

[0008] In order to achieve the above object, this invention relates to amethod for propagating vibration into a conductive fluid, comprising thesteps of:

[0009] preparing a given conductive fluid, and

[0010] applying a given magnetic field and a given wave to theconductive fluid so as to satisfy the relations of:

l _(⊥)>δ  (1)

λ″>λ  (2)

[0011] on condition that the length of the conductive fluid is set tol⊥(m), and the equations of λ=(2/ρμω)^(1/2) and λ″=2πB/ω(ρμ)^(1/2) aredefined (σ: the electric conductivity (S/m) of the conductive fluid, ρ:the density (kg/m³) of the conductive fluid, μ: the permeability of theconductive fluid, B: the strength of the magnetic field (T), ω: theangular frequency of the wave), thereby to generate and propagate agiven vibration into the conductive fluid.

[0012] The inventors had been intensely studied to achieve the aboveobject. Then, they had conceived that by applying an electromagneticforce to a melted conductive fluid such as a liquid metal, instead ofconventionally utilizing a mechanical vibration, an oscillator or aspeaker, a given vibration is generated and propagated in the conductivefluid.

[0013] From the past, it is well known that only a compressional wavecan be propagated into a conductive fluid such as a liquid metal. On theother hand, the vibration originated from the electromagnetic force is atransverse wave. Therefore, in the present invention, the transversewave is generated and propagated in the conductive fluid. As mentionedabove, since it is known that only a compressional wave can bepropagated into the conductive fluid, the inventors had intenselystudied to generate and propagate a transverse wave originated from theelectromagnetic force.

[0014] If a magnetic field of relatively large strength is applied to aconductive fluid, a given disturbance of magnetic field is generated dueto the magnetic field to be applied, and then, propagated in convection.That is, if the conductive fluid is moved under the magnetic field, aninductive current is generated and thus, the distribution of themagnetic field to be applied is changed. In this case, the conductivefluid is moved as the magnetic flux lines are attached to the fluidparticles.

[0015] Then, the inventors found out that by applying the magnetic fieldand a given wave to the conductive fluid under the above-mentionedcondition so that a given requirement is satisfied, a transverse wavecan be generated and propagated into the conductive fluid. As a result,a given vibration can be generated and propagated in the conductivefluid by the electromagnetic force. This invention is realized on thevast researches and developments as mentioned above.

[0016] According to the propagating method of vibration, a givenvibration is generated in a conductive fluid by a given electromagneticforce originated from a magnetic field and a wave. Therefore, without alarge-scale apparatus, the vibration can be easily generated in theconductive fluid. In this point of view, the propagating method of thepresent invention can be preferably employed on a large industrialscale.

[0017] In a preferred embodiment of the present invention, the magneticfield and the wave are applied to the conductive fluid so that therelation (3) of l_(⊥)>λ″ is satisfied. In this case, the intended wavecan be propagated easily in the conductive fluid.

[0018] For example, the propagating method of the present invention canbe preferably utilized for solidifying a melted liquid metal. In thiscase, a given magnetic field and a given wave are applied to the liquidmetal during the solidification process so as to satisfy theabove-requirement according to the present invention. In this case, thesize of the solidification structure can be controlled unrestrainedly,and thus, the solidification structure can be easily fined.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] For better understanding of the present invention, reference ismade to the attached drawings, wherein

[0020]FIG. 1 is a schematic view showing an apparatus which is employedfor solidifying a SnPb alloy according to the propagating method ofvibration of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] This invention will be described in detail with reference to theaccompanying drawings. In the present invention, it is required that agiven magnetic field and a given wave are applied to a conductive fluidso that the above-mentioned relations (1) and (2) are satisfied. Only ifthe relations (1) and (2) are satisfied, the kind of wave and thefrequency of wave are not restricted. In a real process such as thesolidification of a liquid metal, however, since the electricconductivity of the liquid metal is within a range of 10⁵-10⁷S/m and thedensity of the liquid metal is within a range of 10³-10⁴kg/m³, therelations (1) and (2) are satisfied by applying a magnetic field havinga strength within a range of several Tesla through several ten Tesla andapplying a wave having a frequency within a range of several hundred Hzthrough several thousand Hz.

[0022] In this case, a given disturbance of magnetic field is generateddue to the magnetic field to be applied and propagated in convention inthe conductive fluid. That is, the distribution of magnetic field isdetermined by the convection. Therefore, a given transverse wave isgenerated and propagated in the conductive fluid, originated from themagnetic force of the magnetic field and the wave, as mentioned above.As a result, a given vibration can be generated and propagated in theconductive fluid, originated from the transverse wave.

[0023] Such a magnetic field can be generated from a super conductivemagnet. Also, such a wave can be generated from a given external ACpower supply. That is, an AC electric field from the external AC powersupply can be utilized as the wave to be used in the present invention.In this way, the magnetic field and the wave to be utilized in thepresent invention and satisfying the relations (1) and (2) can be easilyobtained from the super conductive magnet and the external AC powersupply, respectively.

[0024] In the present invention, as mentioned above, it is desired thatthe magnetic field and the wave are applied to the conductive fluid soas to satisfy the above-mentioned relation (3). If the strength ofmagnetic field from the super conductive magnet and the frequency ofwave from the AC power supply are controlled appropriately, theabove-mentioned condition can be satisfied.

[0025] It is estimated that the transverse wave propagating in theconductive fluid is an Alfven wave when the relations (1)-(3) aresatisfied. The Alfven wave is being intensely researched in astronomicalphysics and plasma engineering, but not almost done in industrial field.Therefore, the Alfven wave is not almost utilized in the industrialfield. In view of the industrial use of the Alfven wave, too, thepresent invention is quite important.

[0026] The propagating method of vibration of the present invention canbe employed for various industrial fields. Particularly, if the methodis employed for solidifying a melted liquid metal, the solidificationstructure can be controlled freely, and then, fined. In addition, themethod may be employed for degasification, promotion of refiningreaction and control of solid-liquid boundary face configuration.

EXAMPLE

[0027] Next, the present invention will be described concretely onexamples, where the propagating method of vibration of the presentinvention is applied for solidifying a melted metal.

EXAMPLE

[0028] In this example, such an apparatus as shown in FIG. 1 wasemployed, and an alloy having a composition of Sn-10 mol % Pb(hereinafter, called as a “SnPb alloy”) was melted and then, solidified.In the apparatus shown in FIG. 1, a cylindrical vessel 1 (internaldiameter: 30 mm, height: 150 mm) made of glass is employed, andelectrodes 2-1 and 2-2 (each width: 10 mm, each thickness: 2 mm) made ofCu are disposed in the vessel 1 so as to be opposite to one another.Also, an external AC power supply 3 is connected to the ends of theelectrodes 2-1 and 2-2. The vessel 1 including the electrodes 2-1 and2-2 is placed in a super conductive magnet (not shown).

[0029] A SnPb alloy 4 melted was charged in a depth of 120 mm in thevessel 1, and then, the electrodes 2-1 and 2-2 were immersed in themelted SnPb alloy 4 by a length of 20 mm, respectively. Then, a magneticfield of a strength of 8T was applied from the super conductive magnet(not shown) and an AC electric field of a frequency of 2000 Hz and anamplitude of 75 A was applied from the external AC power supply 3 to theSnPb alloy 4. Since the electric conductivity of the SnPb alloy 4 is10⁶-10⁷S/m and the density p of the SnPb alloy 4 is about 10⁴kg/m³, inthis example, the above-mentioned relations (1)-(3) are satisfied by themagnetic field and the AC electric field. Under the condition, the SnPballoy 4 was solidified at a cooling rate of 0.1 K/sec.

[0030] When the solidification structure of the SnPb alloy solidifiedwas observed, the size of the solidification structure was about 1 mm orbelow at both of the upper side and the lower side of the vessel 1.

[0031] When the pressure of a wave propagating in the melted SnPn alloy4 was measured by a sensor provided at the bottom portion of the vessel1, it was turned out to be almost proportion to the current value of theAC electric field applied from the external AC power supply 3.Therefore, during the above solidification process, it was estimatedthat a given Alfven wave was generated and propagated in the melted SnPballoy 4.

COMPARATIVE EXAMPLE

[0032] Except that the magnetic field and the AC electric field were notapplied and thus, a given wave which is estimated as the Alfven wave wasnot propagated, the melted SnPb alloy 4 was solidified in the samemanner as Example. When the solidification structure of the SnPb alloysolidified was observed, the size of the solidification structure wasroughed at both of the upper side and the lower side of the vessel 1.Particularly, at the lower side of the vessel 1, the size of thesolidification structure was enlarged up to about several mm.

[0033] Although the present invention was described in detail withreference to the above examples, this invention is not limited to theabove disclosure and every kind of variation and modification may bemade without departing from the scope of the present invention.

[0034] As mentioned above, only by applying a given magnetic field and agiven electric field to a conductive fluid under a given condition,according to the present invention, a given vibration can be generatedand propagated in a conductive fluid without a large scaled andcomplicated apparatus. Therefore, the propagating method of vibration ofthe present invention may be employed for various industrial fields, andfor example, preferably as a solidification structure controlling methodfor a liquid metal melted.

What is claimed is:
 1. A method for propagating vibration into aconductive fluid, comprising the steps of: preparing a given conductivefluid, and applying a given magnetic field and a given wave to saidconductive fluid so as to satisfy the relations of: l_(⊥)>δ  (1)λ″>λ  (2) on condition that a length of said conductive fluidis set to l_(⊥)(m), and the equations of δ=(2/ρμω)^(1/2) andλ″=2πB/ω(ρμ)^(1/2) are defined (σ: the electric conductivity (S/m) ofsaid conductive fluid, ρ: the density (kg/m³) of said conductive fluid,μ: the permeability of said conductive fluid, B: the strength of saidmagnetic field (T), ω: the angular frequency of said wave), thereby togenerate and propagate a given vibration into said conductive fluid. 2.The propagating method as defined in claim 1, wherein said magneticfield and said wave are applied to said conductive fluid so as tosatisfy the relation of: l _(⊥)>λ″  (3)
 3. The propagating method asdefined in claim 1, wherein said wave to be applied to said conductivefluid includes an AC electric field from an external AC power supply. 4.The propagating method as defined in claim 1, wherein a givendisturbance of magnetic field is generated due to said magnetic field tobe applied and propagated in convection in said conductive fluid.
 5. Thepropagating method as defined in claim 1, wherein an Alfven wave isgenerated and propagated in said conductive fluid.
 6. A method forsolidifying a melted metal, comprising the steps of: preparing a meltedmetal, and applying a given magnetic field and a given wave to saidmelted metal so as to satisfy the relations of: l _(⊥)>δ  (1)λ″>λ  (2)on condition that a length of said melted metal is set to l_(⊥)(m), andthe equations of δ=(2/ρμω)^(1/2) and λ″=2πB/ω(ρμ)^(1/2) are defined (σ:the electric conductivity (S/m) of said melted metal, ρ: the density(kg/m³) of said melted metal, μ: the permeability of said melted metal,B: the strength of said magnetic field (T), ω: the angular frequency ofsaid wave), thereby to generate and propagate a given vibration intosaid melted metal.
 7. The solidifying method as defined in claim 6,wherein said magnetic field and said wave are applied to said meltedmetal so as to satisfy the relation of: l _(⊥)>λ″  (3)
 8. Thesolidifying method as defined in claim 6, wherein said wave to beapplied to said melted metal includes an AC electric field from anexternal AC power supply.
 9. The solidifying method as defined in claim6, wherein a given disturbance of magnetic field is generated due tosaid magnetic field to be applied and propagated in convection in saidmelted metal.
 10. The solidifying method as defined in claim 6, whereinan Alfven wave is generated and propagated in said melted metal.